This invention relates to a meter for measuring the rate of fluid flow such as for determining the rate of fuel usage in an engine.
The efficient functioning of engines comprises an important factor in the operational aspect of trucking firms, marine firms, and other firms which use engine driven equipment. These engines are tested periodically for output efficiency to determine whether or not repair or overhaul is necessary. Various testing methods are used, a common one employing a dynamometer. Another method to determine whether the engine is to be repaired or overhauled is merely by considering total miles run or hours operated. With the use of a dynamometer, or other methods now used, a precise analysis of engine condition is not altogether possible because of variables which may exist from engine to engine such as ignition conditions.
The most efficient method of determining engine condition is to ascertain the amount of fuel consumed by the engine per unit of time. Prior devices have not accomplished this method of testing in a commercially feasible manner because the meters used, while showing fuel usage, do not give a direct reading of the rate that the fuel is used. In prior devices, it is thus necessary to make computations from the meter reading, which of course is inconvenient and many times inaccurate. Another disadvantage of prior devices is that they do not compensate for the expansion or contraction of fuel due to variations in temperature, and thus the fuel is not accurately metered, particularly in slow flow systems such as fuel feed systems for engines. Slow flow systems comprise systems using measuring means with slow flow accuracy defined by the U.S. Bureau of Standards Handbook 44, namely, measuring devices with very slow flow rates and with an accuracy range of .+-. 0.6 of 1 percent throughout the flow range. Although temperature conversion tables are available, based on a temperature constant, for determining volume of flow, such computing method is often inaccurate and always inconvenient. In some cases the use of conversion tables is also impractical.
In view of the above, means heretofore used for determining the condition of engines by ascertaining fuel consumption or miles or hours logged are not considered to be adequate because such means do not indicate with the necessary preciseness the condition of an engine. This may result in overhaul or repair which is not necessary, or on the other hand engines may remain in operation when in fact they should be overhauled or repaired.